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Authors & Affiliations
Viktor Studenyak, Jurgen Jost, Christian F. Doeller, Andrej Bicanski
Abstract
The canonical model of the dentate gyrus (DG) of the hippocampus suggests the DG performs
pattern separation, orthogonalizing similar input patterns [1, 2] aided by an approximate 5-fold expansion of
the cell population relative to its entorhinal cortex inputs [3]. However, more recent experimental results
challenge this standard model, suggesting the DG also supports the precise binding of objects and events to
space and the integration of information across episodes [4]. Very recent studies attribute pattern separation
and pattern integration to anatomically distinct parts of the DG, the suprapyramidal blade and the
infrapyramidal blade respectively [5, 6]. Several models have investigated pattern separation [2], or the role
of adult neurogenesis in the DG [7]. However, none have considered the role of the distinct DG blades. Here
we propose the first computational model that investigates this distinction. In line with recent experimental
work [6, 8] we hypothesise that the suprapyramidal blade contributes to the storage of distinct episodic
memories (via pattern separation and one-shot learning). In contrast, the infrapyramidal blade integrates
information across episodes (learning at a slower rate) to form generalised expectations across episodes,
eventually forming a cognitive map. In the model, both new and old episodes can be compared to these
learned expectations (here, expectations of positions of objects relative to oneself in a spatial layout). This
comparison allows for the calculation of a prediction error, which can drive the storage of poorly predicted
memories and the forgetting of well-predicted memories, thus allowing the hippocampal system to free up
neuronal resources. This allows the model to iteratively build a spatial cognitive map for a familiar
environment on which predictions can be generated by short-scale look-ahead.